The 100th day of classes falls in January or February for most schools, but check with your administrators for an exact date.

Have a party
Hold a party for students to celebrate being 100 days smarter. Give kids 100 popsicle sticks or beads to create something with. Have them estimate the weight of 100 jelly beans, raisins, or marbles.

Help others
Choose a cause students can relate to and ask them to bring loose change or other small donations. Last school year, many schools had students bring 100 pennies for earthquake relief efforts in Haiti.

Get physical
Assist the PE teacher or recess monitors in leading games that reinforce math lessons. Challenge kids to freeze in a silly pose for 100 seconds. Have them do other activities, like dribbling basketballs or doing jumping jacks, in units of 10.